1. Field of the Invention
This invention relates in general to the field of testing for proper assembly of armatures for electric motors, and more particularly to tester equipment for assuring proper alignment between a commutator, a lamination stack, and coil windings for an armature.
2. Description of the Prior Art
In the manufacture of armatures for electric motors, two cylindrical parts called the commutator and the lamination stack are pressed onto a central motor shaft. The commutator and the lamination stack have several radially cut slots running the length of the parts along their outside surfaces. Typically, the commutator and lamination stack must be maintained in angular alignment so that the slots in the lamination stack and the slots in the commutator are aligned within a specified tolerance for proper assembly and operation of the armature. A typical specified tolerance is that these parts are aligned to within plus or minus three degrees from an optimal positioning, or, in other words, within a total tolerance of six degrees.
Prior art devices have been used to test the angular alignment between a commutator and a lamination stack. These prior art devices typically operate by keying on one of the lamination stack slots to locate the armature within the device, and then using an opto-electric sensor to check the angular alignment between a corresponding slot in the commutator. This device requires a sensor, a power supply to drive it, and considerable fixturing and tooling.
Further, in assembling an armature, after the lamination stack, the commutator, and some small insulating parts are in place, a series of coils of insulated wire are typically wound onto the armature assembly using automated equipment, such as, for example, a "double flyer" type of automatic armature winding machine. Using a 16-bar armature as an illustrative example, a typical automatic armature winding machine will hook two wires onto two commutator tangs on opposite diametrical sides of the commutator, and begin winding coils with one wire on each side of the armature wrapped through two lamination stack slots and then back to an adjacent commutator tang. The automated machine will then wind through the next two lamination stack slots and back to the adjacent commutator bar, and then continue winding the rest of the coils until the wire that began at a first commutator bar will terminate at a ninth commutator bar. In this illustrative example, an armature will be completely wound when eight coils are wound on each side.
After winding, it is necessary to determine if the automatic winding machine selected the proper lamination stack slots to wind the wires within. Determination of proper winding of an armature has been done by prior art devices, some similar to the one mentioned above. Typically, the armature is keyed to locate the prior art device about the armature, and a voltage is applied across two commutator bars which are 180 degrees apart to create a magnetic field in the armature similar to one which would be present in actual operation of the armature in a motor. Magnetic sensors are then used to determine the position of the magnetic field created by the coils. If the magnetic field appears in the correct place, then the coils should be properly wound. This prior art device requires a power supply to excite the armature coils, another to excite a magnetic sensor, a magnetic sensor, and considerable tooling and fixturing to perform the test.
The two prior art devices described above are rather costly and require a skilled technician to set up each time an assembly line shifts from making one armature to another. Typically, only the first part in each production run is tested. If the setup on this first part of such an automated process is good, the rest of the parts assembled during the production run should turn out to be good as well.